Such sidepiece ends are known from West German published specification No. 3,237,501 which was published on the Apr. 12th 1984. The problem exists in securing the very soft material of the sheath to the tang, namely not only for the duration of a novelty fair or the duration of trying on at the optician's premises or other short periods under favorable conditions. Rather, the connection must hold even when a thin film of perspiration penetrates into the sidepiece end, which regarded absolutely cannot be prevented if the sidepiece end is worn in an atomosphere with very low or very high temperatures, if the sidepiece end is bent frequently during the life of the spectacle frame, or even if the sidepiece end is brought by oversight to very high temperatures for the purpose of bending, although this was necessary only in the old technique and is no longer necessary with the soft sheaths.
In the case of the sidepiece end according to West German Published Specification No. 3,237,501 the danger exists that in the course of time the longer part of the sheath may twist more or less around the tang. These sheaths have oval cross-section, and then that surface which per se ought to be directed upwards or downwards rests on the head of the wearer. Furthermore even a very low quality demand of spectacle frames requires that the longer part of the sheath should remain connected with the tang and not move in the manner of a stocking for example.